Identification of a regulatory Vδ1 gamma delta T cell subpopulation expressing CD73 in human breast cancer

gamma delta T cells contribute to the immune response against many cancers, notably through their powerful effector functions that lead to the elimination of tumor cells and the recruitment of other immune cells. However, their presence in the tumor microenvironment has been associated with poor prognosis in breast, colon, and pancreatic cancer, suggesting that gamma delta T cells may also display pro-tumor activities. Here, we identified in blood from healthy donors a subpopulation of V delta 1T cells that represents around 20% of the whole V delta 1 population, expresses CD73, and displays immunosuppressive phenotype and functions (i.e., production of immunosuppressive molecules, such as IL-10, adenosine, and the chemotactic factor IL-8, and inhibition of alpha beta T cell proliferation). We then found that in human breast tumors, gamma delta T cells were present particularly in late stage breast cancer samples, and that similar to 20% of tumor-infiltrating gamma delta T cells expressed CD73. Taken together, these results suggest that regulatory gamma delta T cells are present in the breast cancer microenvironment and may display immunosuppressive functions through the production of immunosuppressive molecules, such as IL-10, IL-8, and adenosine, thus promoting tumor growth.